Hydraulic systems are particularly useful in applications requiring significant power transfer and are extremely reliable in harsh environments, for example, in construction and industrial work places. Earthmoving machines, such as excavators, backhoe loaders, and wheel type loaders are a few examples where the large power output and reliability of hydraulic systems are desirable.
Typically, a diesel or internal combustion engine powers the hydraulic system. The hydraulic system, in turn, delivers power to the machine's work implement. The hydraulic system typically includes a pump for supplying pressurized hydraulic fluid and a directional valve for controlling the flow of hydraulic fluid to a hydraulic motor which in turn delivers power to a work attachment, e.g., a bucket.
Conventionally, such earth working machines include a mechanical cushion within the hydraulic cylinders to ease the shock when the hydraulic cylinder piston strikes a stroke end of the cylinder. Typically, an operator displaces a lever device to control the velocity of the hydraulic cylinder piston. If the operator fully displaces the lever, causing the piston to strike the stroke end, the mechanical cushion cannot completely absorb the inertial force of the impact, which subjects the cushion chamber to high pressures, adversely affecting the durability of the cylinder and leading to higher structural cost. In addition, the impact causes the machine body to shake, which can lead to operator discomfort.
The present invention is directed toward overcoming one or more of the problems as set forth above.